According to a fresh status report, PST no longer considers the threat to be as high as assessed in April, when the probability of an attempted terrorist act was changed from "possible" to "likely".

The decision to lower the risk level was made after considering recent changes in the threat picture, the report said.

There has been found a lower degree of organized radicalization into extreme Islamism. In addition, there are few foreign warriors traveling out of the country and few who have returned recently to Norway.

However, there is still serious terrorist threat in many other Western countries, the report said.

The Islamic State "has earlier used refugee routes to deploy operators in Europe. This will be a sustained challenge for all countries in Europe, regardless of the specific threat that individual countries are exposed to," the report said.

PST added that Norway "is still considered a part of the enemy image by international terrorist groups, and there are extreme Islamists who can follow the instructions of international terrorist groups."

According to PST, a possible terrorist act in Norway would be of the same kind as it has seen elsewhere in Europe, which implies use of knife and vehicle against targets with few security measures but many civilians around.

"Attacks with relatively simple means against easily accessible targets are often characterized by short preparation time and limited opportunities to prevent or avert them in advance, with perpetrators intending to become martyrs. Response time and capability are essential to limit the extent of such attacks," PST said.